This invention relates to ink applicator arrangements. The invention relates more particularly to an improved means for applying developer ink to an imaged area in a reproduction system.
In various reproduction and copying systems, it is desirable to apply a developer ink to an image or record medium. More particularly, in one form of electrostatic copying process, a latent image is established electrostatically on an image retention surface with a liquid developing material. The developing material adheres to the surface and conforms to the image. The image is transferred to a record medium for recording, or alternatively, the image retention surface may itself comprise a record medium.
In one image development process sometimes termed polar liquid development, a developer ink is delivered to the image retention surface by a dispensing body. The liquid ink transfers from the dispensing body to the retention surface by virtue of electrostatic forces established by charged areas on the image retention surface. The dispensing body generally comprises a roller having a surface which contacts the image retention surface and which includes an array of lands and grooves. The dispensing body is inked so as to provide a supply of ink which is contained in the grooves of the dispensing body. When the surface of the dispensing body is brought into contact with the surface bearing latent electrostatic image, the liquid development ink transfers from the grooves to the image retention surface by virtue of electrostatic forces exerted on the polar ink.
It has been found that it is particularly advantageous to apply a developer liquid in an electrophotographic process by means of a developing roller consisting of a cylindrical member which has been provided with superficial parallel or thread-like grooves wherby the grooves are arranged substantially perpendicular to the axis of rotation of the development roller. This type of applicator is made by winding an adhesive-coated synthetic resin monofilament under carefully controlled conditions at a predetermined pitch onto a cylindrical rubber substrate. The substrate generally consists of a steel mandrel covered with a layer of conductive elastomeric material. The concept behind such a filament-wound applicator is that the hard filaments can be individually displaced into a soft rubber roll thereby forming a uniform set of lands for the applicator.
In the manufacture of filament-wound applicator rolls for use in liquid development xerography, several problem areas have been identified. One is the need for adequate bonding of a synthetic resin filament such as nylon to the conductive elastomeric substrate during the winding process. Yet another is the proper indexing of the filament thread along the cylindrical roll so that uniform peaks and valleys occur across the developer cylinder. The application of adhesive to the filament just prior to winding to secure the material to the mandrel has been attempted with mixed results. In some cases the coating is not sufficiently bonded to the resin filament so that undesirable flaking occurs. Also application of abundant adhesive just prior to winding causes the adhesive to fill the valleys of the roll thereby also coating the conductive elastomeric material, the conductivity of which is critical to polar ink development. There is a serious need to develop an adhesive coating material which upon application will not coat the conductive elastomeric material in the winding valleys and also does not ultimately flake.